Different from page numbering from the second page, you need to insert section breaks to start page numbering from the third page (or any later pages). Please see the steps below for details:
Part I: Insert Page Number
Step 1: Click the "Insert" tab from the ribbon;
Step 2: Click "Page Number" from the "Header&Footer" area;
Step 3: Select the page number location and format.
Part II: Insert Section Break
Step 1: Click anywhere in the content to move the cursor out of the header or footer area, then move the mouse cursor to the end of the second page;
Step 2: Click the "Breaks" command from the "Layout" tab in the ribbon, then click "Next Page" from the drop-down list;
Step 3: Click on the number "3" on page three and click on "Link to Previous" in the "Header & Footer" tab from the ribbon (or the Design tab in some Excel versions).
Part III: Format Page Number
Step 1: Right click on number "3" again and select "Format Page Numbers";
Step 2: In the new dialog box, change (or type in) number "1" in the "Start at" box and all page numbers from page three are changed to numbering from "1";
Step 3: You can delete the page numbers in the first two pages to have them empty.
Please repeat the steps above if you want to start page numbering in a later page such as page 4 or page 5.